1. Field of the Invention
The present invention relates to an impedance conversion circuit that makes an impedance including an inductance and an integrated circuit including thereof.
2. Description of the Related Art
It is difficult to make a desired impedance, especially an inductance within a semiconductor integrated circuit.
Japanese Patent Laid-open No. Hei 11-205087 discloses an impedance conversion circuit using a plurality of operational amplifiers as shown in FIG. 25 as a circuit that makes an impedance including an inductance.
In this impedance conversion circuit, impedances Z1, Z2, Z3, Z4, and Z5 are connected in series with each other between an input terminal 91, which is supplied with an input signal voltage Vin, and a ground. The input terminal 91 and a connection node of the impedances Z2 and Z3 are connected to the non-inverting input terminal and the inverting input terminal of an operational amplifier 92. The output terminal of the operational amplifier 92 is connected to a connection node of the impedances Z3 and Z4. A connection node of the impedances Z4 and Z5 and a connection node of the impedances Z2 and Z3 are connected to the non-inverting input terminal and the inverting input terminal of an operational amplifier 93. The output terminal of the operational amplifier 93 is connected to a connection node of the impedances Z1 and Z2.
In the impedance conversion circuit, as shown in FIG. 25, an impedance Zin as viewed from the input terminal 91 isZin=(Z1·Z3·Z5)/(Z2·Z4)  (91)